1. Field of the Invention
This invention relates to photonic band gap technology.
2. Related Art
In recent years, advances in photonic technology have generated a trend toward the integration of electronic and photonic devices. These devices offer an array of advantages over conventional electronic devices. For example, they can provide enhanced speed of operation and reduced size. In addition, these devices provide robustness to environmental changes, such as rapid temperature variations, increased lifetime, and the ability to handle high repetition rates. These structures can be made of metals, semiconductor materials, ordinary dielectrics, or any combination of these materials.
In photonic band gap (PBG) structures, electromagnetic field propagation is forbidden for a range of frequencies, and allowed for others. The nearly complete absence of some frequencies in the transmitted spectrum is referred to as a photonic band gap (PBG), in analogy to semiconductor band gaps. This phenomenon is based on the interference of light. For frequencies inside the band gap, forward-propagating and backward-propagating signal components can destructively cancel inside the structure, leading to complete reflection.
For example, recent advancements in PBG structures have been made in the development of a photonic band edge nonlinear optical limiter and switch. See M. Scalora, et al., Optical Limiting and Switching of Ultrashort Pulses in Nonlinear Photonic Band-Gap Materials, Physical Review Letters 73:1368 (1994) (incorporated herein by reference in its entirety). Also, advancements in photonic technology have been achieved with the development of the nonlinear optical diode. See M. Scalora et al., The Photonic Band-Edge Optical Diode, Journal of Applied Physics 76:2023 (1994) (incorporated by reference herein in its entirety). In addition, the physical processes involved in the photonic signal delay imparted by a uniform PBG structure are described in detail in Scalora et al., Ultrashort Pulse Propagation at The Photonic Band Edge: Large Tunable Group Delay with Minimal Distortion and Loss, Phys. Rev. E Rapid Comm. 54(2), R1078-R1081 (August 1996) (incorporated by reference herein in its entirety).
What is needed is a device that performs phase shifting of an electromagnetic signal that is compact in size, performs with low intensity input signals, and can be manufactured by conventional techniques.
The present invention generally relates to a device and method of creating an optical signal phase shift using a compact and readily made structure. For example, this structure may have a length that is less than 10 micrometers. This compact structure enables phase shifts of order xcfx80 for low intensity input signals.
According to one embodiment of the present invention, a device is provided for generating a photonic signal having a phase different from an input photonic signal that is incident on the device. The input photonic signal has a signal frequency, a signal bandwidth, and a signal intensity. The device comprises a plurality of material layers. The material layers are arranged such that the device exhibits a photonic band gap structure. The photonic band gap structure exhibits a transmission band edge that corresponds to the input photonic signal frequency. A second photonic signal is generated at a second photonic frequency preferably close to a second band edge. The interaction of the input photonic signal with the second photonic signal generates a phase shift of order xcfx80 for relatively small input intensities. The interaction of the input photonic signal with the arrangement of layers generates a phase shift.
The plurality of material layers can include a plurality of first material layers and a plurality of second material layers. The first and second material layers can be arranged in a periodically alternating manner or in an aperiodic manner such that the arrangement formed therefrom exhibits the photonic band gap structure. The first material layer can have a first index of refraction and the second material layer can have a second index of refraction that is different from the first index of refraction. Also, the first material layer can have a first thickness and said second material layer can have a second thickness that is different from the first thickness. These first and second material layers can respectively comprise Al2O3 and Al30%Ga70%As semiconductor layers, where these layers are formed on a semiconductor substrate or a dielectric substrate.
The first photonic signal can be tuned at the first resonance near the first band edge of the band gap structure and the second photonic signal can be tuned at the first resonance near the second band edge of the band gap structure. Moreover, the first and second photonic signals can be phase mismatched.
Further embodiments, features, and advantages of the present inventions, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.